(1) Field of the Invention
The present invention relates to an electrode plate production method and a battery production method.
(2) Description of the Related Art
The process of producing an electrode plate used in a battery represented by an alkaline secondary battery includes a process in which a plate-shaped core body of an electrode plate is filled with an active material densely and broadly. However, the filled active material may remove from the core body while the battery is kept to be used. The active material is difficult to remove from the central part of the core body (active material filling area) since the central part is covered with a separator or the like, but is easy to remove from the circumferential part of the active material filling area since the end surfaces of the circumferential part are exposed to outside. Also, the electrode plate production process may include a step in which the active material is filled into a prototype of the core body and then the prototype is cut into pieces of a predetermined size. In the active material filling area after the cutting step, the bonding force between the conductive core body and the active material particles and between the active material particles is weaker at the cutting surfaces and their vicinities than at the central part of the active material filling area. This makes the active material easy to remove from the vicinities of the cutting surfaces even if a large external force is not given. When this happens, the content amount of the active material decreases, and the battery capacity decreases. At the same time, the removed active material may bridge between the positive and negative electrode plates to cause an electrical short circuit to occur.
To cope with this problem, the following methods, for example, have been proposed to restrict the removal of the active material from the active material filling area: a method of covering the circumferential part, where the removal is easy to occur, of each electrode plate with tape (Japanese Patent Application Publication No. 3-159074); a method of covering the circumferential part with a thermal-adhesive resin (Japanese Patent Application Publication No. 5-190200); and a method of applying a resin solution to the circumferential part of the electrode plate (Japanese Utility Model Application Publication No. 63-85869).
In the case of the method of covering the circumferential part with tape, first the prototype of the electrode plate is cut and then the circumferential part is covered with tape. Also, in the case of the method of covering the circumferential part with a thermal-adhesive resin, it is necessary to attach a thermal-adhesive resin film to the circumferential part. However, such methods have some problems. For example, if the tape is unsteady and at least one surface thereof is adhesive, the tape may be distorted during the step of attaching the tape and adhesive portions may be bonded together. Also, in the case of the method of applying the resin solution, there is a problem that it takes time before the applied solution is dried. Accordingly, there is room for improving the production process in these methods.